For example, with respect to an information recording medium, such as a Compact Disc-Read Only Memory (CD-ROM), a Compact Disc-Recordable (CD-R), and a DVD-ROM, an information recording medium, such as an optical disc, of a multi-layer type or of a dual-layer-type in which a plurality of recording layers are laminated or pasted on the same substrate has also been developed, as described in patent documents 1 and 2 and the like. Moreover, on an information recording apparatus, such as a DVD recorder, which records information onto such a dual-layer type optical disc, i.e. a two-layer type optical disc, laser light for recording is focused on a recording layer which is on the nearest side observed from the irradiation side of the laser light (i.e. on the closest side to an optical pickup) (wherein the recording layer is referred to as a “L0 layer”, as occasion demands). By this, the information recording apparatus records the information into the L0 layer in an irreversible change recording method by heat or in a rewritable method. Moreover, the laser light is focused on a recording layer which is on the back of the L0 layer observed from the irradiation side of the laser light (i.e. on the farthest side from the optical pickup), through the L0 layer and the like (wherein the recording layer is referred to as a “L1 layer”, as occasion demands). By this, the information recording apparatus records the information into the L1 layer in the irreversible change recording method by heat or in the rewritable method.    patent document 1: Japanese Patent Application Laid Open NO. 2000-311346    patent document 2: Japanese Patent Application Laid Open NO. 2001-23237